In modern internal combustion engines, use is made of devices for variably adjusting the control times of gas-exchange valves in order to be able to variably adjust the phase relationship between a crankshaft and a camshaft or at least one cam of a camshaft in a defined angle range between a maximum early position and a maximum late position. For this purpose, the device is integrated into a drivetrain which serves to transmit torque from the crankshaft to the camshaft. Said drivetrain may for example be realized as a belt drive, chain drive or gearwheel drive. Here, devices are known which act on the phase position of all cams of a camshaft. Devices are likewise known which are attached to a camshaft and which are composed of an outer hollow shaft and an inner shaft which is arranged concentrically with respect to said hollow shaft. In this context, a first group of cams is rotationally fixedly connected to the hollow shaft while a second group of cams is rotationally fixedly connected to the inner shaft. In this embodiment, the device may for example act on only one of the two groups, while the phase position of the other cams remains constant. Devices are likewise conceivable which make it possible to vary the phase positions of both groups of cams independently of one another.
DE 10 2005 014 680 A1 discloses an adjustable camshaft, at the two ends of which is arranged a device for variably adjusting the control times of gas-exchange valves. The adjustable camshaft is composed of shafts which are mounted concentrically one inside the other and which can be adjusted relative to one another in terms of rotational angle and which are drive-connected to at least one of the devices each.
A disadvantage of said embodiment is that the mounting of the concentrically arranged shafts with respect to one another takes place directly via the shafts. For this purpose, complex and expensive machining steps are required, for example on an inner lateral surface of the outer hollow shaft and on a counterpart bearing point, which is aligned with fitting accuracy with respect to said inner lateral surface, on the inner shaft.